Universität Augsburg
Institut für Mathematik

Please ask Prof. Urs Frauenfelder for­ login details.

Periodic Hamiltonian flows are protagonists of fascinating rigidity and flexibility phenomena: Bertrand proved in 1873 that the only central forces for which all bounded orbits are periodic are given by the harmonic and the gravitational potential; on the other hand, Guillemin constructed in 1976 an infinite-dimensional family of Riemannian metrics on the two-sphere, whose geodesics are all periodic. In this talk, we will focus on periodic Hamiltonian flows in the class of magnetic systems on surfaces where rigidity and flexibility coexist. This is joint work with Luca Asselle (University of Giessen).